Early merchant and diverse other vessels - Naval warfare and warships - Ancient and Medieval - Mediterranean and Indian Ocean - Atlantic and Pacific.

Tuesday, July 14, 2015

Roman Shipboard Weapons II

Grapnels such as this, attached to lengths of rope, were thrown to
ensnare an enemy ship and to pull it close enough to enable it to be boarded. A
variation of this was attached to a shaft (the harpax) which could be shot from
an artillery piece for longer range. Iron grapnel, second century AD.

Boarding

Before the Punic Wars Roman naval activity had for the most
part been carried out by a modest numbers of smaller ships, against like
opponents and boarding an enemy vessel had been an ad hoc affair. In the great
wars, large numbers of big ships carrying tens of thousands of men were engaged
and pitted against an enemy, initially superior in seamanship to the majority
of the Roman ships. Additionally, far larger contingents of marines were
carried who, to be effective, had to have some means of crossing to an enemy
deck, while themselves being under attack.

If ships lay close alongside each other, marines were able
to clamber across the gap along the ship’s length. The Carthaginians preferred
ramming attacks and so the gap across their bows was too great to jump. The
Roman solution was to mount a ‘bridge’ 36 feet long (11 m) and 4 feet wide (1.2
m) with a slot in one end which fitted around a post 24 feet in height (7.3 m)
mounted in the foredeck; the bridge was hauled up by rope and pulley, to be held
almost vertically against the post. At the other, free end of the bridge was a
metal spike (the actual corvus, raven’s beak) the slot allowed the bridge to be
adjusted as to length and swung from side to side, so that when the Roman ship
came within range, the bridge was dropped across the enemy deck, into which the
corvus embedded itself, locking the ships together. The bridge was wide enough
for men to cross two abreast and, covered by missiles shot from their towers,
the Roman marines could swarm across. The bridge had a low rail on each side to
knee-height and the soldier’s shields covered them from knee to shoulder, so is
was preferable to pass starboard to starboard of the enemy and drop the corvus
so the marines would cross with their shielded sides to the enemy. The
equipment was bulky and could only be mounted on the big quinqueremes.

Although outstandingly successful in action, the drawback
was that the corvus was heavy and mounted high in the very bows, it added
considerable top weight and adversely affected sea-keeping qualities. The loss
of so many ships equipped with it in storms led to the device being discarded
by about 250 BC and being replaced by an alternative form of ‘boarding bridge’.
No description of this device survives but it was lighter and able to be
dismantled and stowed on deck, or even jettisoned if necessary, in effect a
lightweight corvus, able to be manhandled without the need for the heavy post
and tackle.

Artillery

Artillery was a feature of ancient warships almost from its
invention in the early fourth century BC. At that time the engineers of
Dionysius, the tyrant of Syracuse, made a large composite bow, larger and more
powerful than could be drawn by a man, this they mounted on a timber stock,
together with a winch and trigger mechanism to draw and release it. The whole
was connected to a stand by a universal joint which enabled the machine to be
trained both vertically and horizontally and thereby aimed. The stock to which
the bow was fixed had a central channel along the top in which was fitted a
slider with the trigger mechanism and a channel for the missile; this was
locked to the bowstring and the whole slider pulled back by the winch, checked
by a ratchet along the sides of the stock. Upon release of the missile, the
slider was pushed forward, to re-engage the bow string and winched back again
to reload. These machines could hurl a large arrow or, with an adaptor, a stone
shot, up to 300 yards (275 m). Mounted on ships, they could cause devastation
if shot among an enemy’s rowers, easily piercing the leather screens which had
been sufficient to stop javelins or arrows and which had provided their
protection up to then; the advent of artillery led to the progressive boxing in
of the rowers, to provide them with sufficient armour protection.

Reliable and simple to maintain, these machines were in use
until about 240 BC; before that, the engineers of Philip II of Macedon (reigned
359–336 BC) had perfected a new type of propulsion system for artillery. The
composite bow was replaced by two short bow staves, each inserted into a skein
of animal sinew which had been woven into cords, stretched, oiled and twisted
to form torsion springs which stored great power. These were mounted in special
carriers and kept in tension by passing them through a hole and washer at the
top and bottom and retained by a bar; they were mounted each side of a stock
with slider and trigger, similar to their predecessors. Being a good deal more
powerful, range was increased to some 400 yards (366 m) and they could be made
in ever increasing sizes. The springs were susceptible to damp and needed to be
regularly removed and restretched and oiled, requiring in turn, specialised
artillery artificers. As the pieces were made by estimating, with no set pattern
of parts, performance could vary greatly, which is why the earlier form
continued in use.

From about 275 BC Ptolemy of Egypt’s engineers had developed
a formula for building torsion spring artillery pieces. Starting with the
length of arrow that the intended machine was to shoot, the formula dictated
the fraction of that length (it was 1/9th) which was to be the diameter of the
holes in the carrier through which the springs would pass. All dimensions of
all of the components of the machine were then dictated by the formula, as
multiples or fractions of that hole diameter. These ‘formula machines’ proved
to be reliable, of known performance and could be mass produced in standard
sizes.

These machines supplanted the earlier types and became
standard equipment aboard warships. The smallest type seen to mount artillery
was the trireme, whereas quinqueremes and larger types could carry up to ten.
The larger ships could also carry larger sizes of catapult. These weapons,
although capable of inflicting damage to crew and ship, were not ‘ship
destroyers’, and the modestly sized and well attested three-span (shooting an
arrow 27 inches in length (685 mm) with a stock length of 4 feet 6 inches (1.27
m) and two-cubit (3-foot or 915 mm arrow) with a stock length of 6 feet (1.83
m) machines would have been ideal as anti-personnel weapons.

Apart from shooting at each other, warships could bring
their artillery to bear in support of an opposed troop landing, as Caesar’s
ships did in Britain in 55 BC and again in his attack on the Heptastadion at
Alexandria in 47 BC. Artillery on ships could also be used as floating
batteries, as was done to cover the building of a bridge over the Euphrates in
AD 62.

Apart from the normal complement of arrow and stone
shooters, larger machines were on occasion, mounted for siege or assault work,
especially during the Punic Wars. Siege artillery was substantially larger and
predominantly stone throwers, the very biggest being capable of hurling a stone
shot weighing an amazing 260 pounds (118 kg). Although siege machines smaller
than this were mounted, the additional weight of the machine and of its stone
shot had to be considered. The weight of a three-span piece has been estimated
at about a hundredweight (112 lb, 61.7 kg) and that a quinquereme could carry
ten, plus a couple of small stone throwers and still have its normal complement
of forty marines. Clearly the installation of such machines had to be offset by
weight savings, the marines being replaced by artillerymen and the rowing crew being
reduced to just enough to manoeuvre the ship into position and all stores
landed.

As examples of this practice, in 210 BC, the Roman fleet
supported an assault upon Naupactus from seaward using siege artillery. A year
later, in 209 BC, both war- and merchant ships were so equipped for the siege
of Taranto and warships with extra artillery joined the assault on Cartagena.
Finally, Scipio put siege artillery aboard his warships for a feint against
Utica in 204 BC.

Grapnels attached to a line and thrown, had long been in use
to ensnare and pull an enemy ship in so that it could be boarded but for the
war against Sextus (38–36 BC) Octavian’s admiral Agrippa introduced the harpax
(harpoon), a grapnel attached to the end of a shaft 7.5 feet in length (2.3 m.)
and lined with metal strips so that it could not easily be cut through. It was
shot from the larger onboard catapults and trailed a line which could be hauled
in. Although the range of the machine was considerably reduced by the added
weight of the missile and the drag of the line, it could still far outrange any
hand-thrown grapnel.

Artillery was not mounted on towers which, being
comparatively flimsy, could not support the weight or the shock of discharge of
the machines. Further, the position of the universal joint mounting, close
behind the spring-carrier frame, prevented the piece from being depressed to
shoot down on to an enemy deck. Low platforms for artillery were sometimes
erected on deck to give an elevated position and enable them to shoot on either
beam.

In the late first century AD there was a radical redesign of
the smaller types of artillery pieces which resulted in replacing the former
wood and iron spring assemblies with finely made all-metal parts for the
torsion spring carriers and their mounting frame. Although more complex and
requiring more specialised manufacture, they could be dismantled and worn or
damaged parts quickly replaced, the parts being standardised and
interchangeable. They were more compact and also more powerful, range being
increased to in excess of 500 yards (457 m). These are the machines so much in
evidence on Trajan’s Column. Light, compact and powerful, these machines were
ideal for mounting on warships, including many of those too small to have
carried the earlier types.

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